Segment Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 25, 2016	Sep. 25, 2016	Jun. 26, 2016	Mar. 27, 2016	Dec. 27, 2015	Sep. 27, 2015	Jun. 28, 2015	Mar. 29, 2015	Dec. 25, 2016	Dec. 27, 2015	Dec. 28, 2014
Segment Reporting Information [Line Items]
Total revenues									$ 668.7	$ 657.1	$ 763.0
Percentage of foreign revenue to total revenue (as a percent)									12.00%	11.00%	12.00%
Litigation related charges									$ 1.7	$ 0.0	$ 0.0
Operating income (loss)	$ 4.6	$ (13.0)	$ 0.0	$ (10.2)	$ 1.5	$ 1.6	$ (3.7)	$ (3.9)	(18.6)	(4.5)	5.3
Unmanned Systems
Segment Reporting Information [Line Items]
Loss accrual									18.7
Costs related to retrofits										5.7	3.1
Public Safety & Security
Segment Reporting Information [Line Items]
Litigation related charges									1.9
Integration Project Expense									4.1
Kratos Government Solutions
Segment Reporting Information [Line Items]
Assets of foreign subsidiaries	$ 113.7				$ 106.2				113.7	106.2	115.5
Business Exit Costs									9.2
Corporate activities
Segment Reporting Information [Line Items]
Operating income (loss)									(5.2)	(7.0)	(4.4)
Non-US
Segment Reporting Information [Line Items]
Total revenues									$ 80.1	$ 73.2	$ 89.0